CI: Exclude MbedTLS subtree for CONFIG checks

Since MbedTLS is an external repo with its own coding style,
exclude it from Azure and gitlab CI CONFIG checks.

Signed-off-by: Raymond Mao <raymond.mao@linaro.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
diff --git a/.azure-pipelines.yml b/.azure-pipelines.yml
index 93111eb..b66d49a 100644
--- a/.azure-pipelines.yml
+++ b/.azure-pipelines.yml
@@ -76,7 +76,8 @@
       # have no matches.
       - script: git grep -E '^#[[:blank:]]*(define|undef)[[:blank:]]*CONFIG_'
                   :^doc/ :^arch/arm/dts/ :^scripts/kconfig/lkc.h
-                  :^include/linux/kconfig.h :^tools/ :^dts/upstream/ &&
+                  :^include/linux/kconfig.h :^tools/ :^dts/upstream/
+                  :^lib/mbedtls/external :^lib/mbedtls/mbedtls_def_config.h &&
                   exit 1 || exit 0
 
   - job: docs